Subbing compositions for hydrophobic film support



United States Patent SUBBING COMPOSITIONS FOR HYDROPHOBIC FILM SUPPORT Kenneth W. Scott, Sterling S. Sweet, and Maurice H. Van Horn, Rochester, N. Y., assignors to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey No Drawing. Application June 25, 1953, Serial No. 364,198

7 Claims. (Cl. 106-135) This invention relates to the subbing of photographic film and more particularly to a novel subbing composition containing gelatin, casein or zein dissolved in trifluoroacetic acid which composition may be employed to sub-coat various hydrophobic film supports.

In the manufacture of photographic film in which the film support is formed of cellulose triacetate, for example, of those compositions such as described in U. S. Patents 2,469,395 of May 10, 1949 and 2,582,049 of January 8, 1952, or other such hydrophobic material, such as polyethylene terephthalate film support, difiiculty is often experienced in obtaining satisfactory adhesion of the emulsion and other layers to the hydrophobic surface. The degree of adhesion of the layers to the film support must be neither too great, in which case the resulting photographic film is brittle, nor too slight, in which case the layers of the film strip or peel from the hydrophobic support.

Generally, the emulsion, or photosensitive layer, is usually composed of a hydrophilic substance such as gelatin which contains photo-sensitive chemicals. However, if such an emulsion layer is coated directly onto such a hydrophobic film support, as mentioned above, there will be an unsatisfactory adhesive bond between the hydrophobic and hydrophilic surfaces and separation will easily occur.

It is customary, therefore, to employ a subbing layer which will adhere satisfactorily to both the emulsion layer, or other hydrophilic layer, and to the hydrophobic film support surface.

Gelatin-containing or other polypeptide-containing subbing layers are particularly advantageous from various standpoints and it is an object, therefore, of the present invention to provide a gelatin, casein, or zein subbing composition which will readily adhere to hydrophobic film support surfaces, but which will itself provide a hydrophilic surface to which other hydrophilic layers kill adhere firmly. Other objects will appear hereina ter.

In accordance with the present invention we have found that a dilute solution of gelatin, casein or zein in tri-fiuoroacetie acid when coated onto such a hydrophobic film support and dried provides a tightly adherent foundation for subsequent coatings of the hydrophilic photographic vehicle. When the subbing solution contains only gelatin and trifluoroacetic acid, an aqueous solution of the acid may be employed if desired.

Our invention will be further illustrated in the following examples.

Example 1 A film support of cellulose triacetate having an acetyl content of 43.5% was coated with a gelatin-trifluoroacetic acid solution containing 1% gelatin. The thus coated support was dried uniformly for 1 hour at 70 C. and then overcoated with a gelatin-silver halide emulsion layer. Satisfactory adherence of the emulsion layer to the cellulose triacetate film support by means of the intermediate gelatin subbing layer was shown by adherence tests.

Example 2 Another film support of cellulose triacetate having an 2,703,290 Patented Mar. 1, 1955 sion layer. The film produced in this manner was found to be free from objectipnable stripping and brittleness and the subbing layer did not retain a large amount of solvent after drying.

Example 3 One percent gelatin in 50:50 mixture by weight of trifluoroacetic acid and methyl alcohol was coated on cellulose acetate film support, dried, and overcoated with a layer of gelatin which adhered satisfactorily.

Example 4 A 1% solution of gelatin in trifluoroacetic acid was coated on a polyethylene terephthalate film support and dried for 1 hour at 70 C. This subbing layer was overcoated with a gelatin-silver halide emulsion. Excellent adherence of the layers resulted.

Example 5 A 1% solution of zein in trifluoroacetic acid was coated on a polyethylene terephthalate film support and dried for 1 /2 hours at 70 C. This subbing layer was coated with a gelatin-silver halide emulsion. Satisfactory adherence of the layers resulted.

Example 6 Example 7 One percent casein in trifluoroacetic acid was coated on cellulose acetate film base, dried, and overcoated with a layer of gelatin, which adhered satisfactorily.

The gelatin, casein or zein subbing solutions and the emulsion coating may be coated onto the film support by any satisfactory coating process. Such processes include immersion of the surface of the film into a solution of the solution, spraying, bead coating or coating from a hopper.

The photographic film produced according to our invention is satisfactory and meets customary requirements. It is not subject to stripping and is sufficiently flexible to meet customary requirements of commercial photographic film.

We claim:

1. A composition of matter suitable for the sub-coating of a hydrophobic film support which comprises approximately 1% by weight of a compound selected from the group consisting of gelatin, casein and zein dissolved in a solution consisting essentially of trifluoroacetic acid.

2. A composition of matter suitable for the sub-coating of cellulose triacetate film support which consists essenially of 1% of gelatin dissolved in trifluoroacetic aci 3. A composition of matter suitable for the sub-coating of polyethylene terephthalate film support which consists essentially of 1% of gelatin dissolved in trifluoroacetic acid.

4. A composition of matter suitable for the sub-coating of cellulose triacetate film support which consists essentially of 1% casein dissolved in trifluoroacetic acid.

5. A composition of matter suitable for the sub-coating of polyethylene terephthalate film support which consists essentially of 1% casein dissolved in trifluoroacetic aci 6. A composition of matter suitable for the sub-coating of cellulose triacetate film support which consists essentially of 1% of zein dissolved in trifluoroacetic acid.

7. A composition of matter suitable for the sub-coating of polyethylene terephthalate film support which consists essentially of 1% of zein dissolved in trifluoroacetic aci References Cited in the file of this patent UNITED STATES PATENTS 2,662,023 Arthur et al Dec. 8, 1953 

1. A COMPOSITION OF MATTER SUITABLE FOR THE SUB-COATING OF A HYDROPHOBIC FILM SUPPORT WHICH COMPRISES APPROXIMATELY 1% BY WEIGHT OF A COMPOUND SELECTED FROM THE GROUP CONSISTING OF GELATIN, CASEIN AND ZEIN DISSOLVED IN A SOLUTION CONSISTING ESSENTIALLY OF TRIFLYOROACETIC ACID. 